1. Field of the Invention
The present invention relates to thermosensitive recording materials having excellent thermal response, having minimized adhesion to a thermal head and minimized background fogging due to heat accumulation on a thermal head.
2. Discussion of Related Art
Thermosensitive recording materials are generally composed of a support having provided thereon a thermosensitive recording layer containing as major constituents an ordinarily colorless or slightly colored dye precursor and an electron receptive developer. Upon being heated by means of a thermal head, thermal pen or laser beam, the dye precursor instantaneously reacts with the developer to form a recorded image, as disclosed in Japanese Patent Examined Publication Nos. 4160/68, 14039/70, etc. Because of the advantages of relatively simple design of devices and easy maintenance, the recording devices employing such thermosensitive recording materials are being used in a wide field including recording instruments for measurements, facsimiles, printers, terminal devices for computers, labels, and automatic vending machines for railroad tickets and the like. Particularly in the field of facsimiles, demand for thermal sensitive mode has been greatly increasing and the performance of facsimiles has become high speed due to reduction in transmission costs. In response to such high speed performance required for facsimiles, high sensitivity of thermosensitive recording materials has been demanded. On the other hand, in thermosensitive recording materials, an electron donating dye precursor and an electron receptive developer melt upon heating with a thermal head to form a color and the melted material may adhere to the thermal head on some occasions, resulting in damaging the head or deteriorating the quality of the printed characters.
As a countermeasure, it is disclosed in Japanese Patent Unexamined Publication No. 86229/78 to incorporate pigments having high oil absorption. It is also disclosed in Japanese Patent Unexamined Publication Nos. 23545/79, 25845/79 and 0704/79 to provide an intermediate layer between a support and a thermosensitive recording layer.
However, these compositions do not necessarily achieve the desired effects.